Hollow-core fiber photothermal methane sensor with temperature compensation

We demonstrate a high sensitivity all-fiber spectroscopic methane sensor based on photothermal interferometry. With 2.4-m-long anti-resonant hollow-core fiber, 1654 nm distributed feedback laser, and Raman fiber amplifier, noise-equivalent concentration of ∼ 4.3 p mathvariant="normal">b is achieved at the room temperature pressure 1 mathvariant="normal">a mathvariant="normal">r . The effects phase modulation as well stability interferometer are studied. By introducing temperature-dependent compensation factor stabilizing quadrature, signal instability 2.1 mathvariant="normal">% demonstrated for variation from 296 to 373 K.